I just watched Tina Fey's impression of Sarah Palin on Hulu. The impression was deadly accurate. She got the accent, the R's, and the dialogue was cribbed from Palin's real-life endorsement speech, a sign from Fey and the SNL writers that their gifts for satire can't add to anything that's already there. Larry David's Bernie Sanders is only slightly more imaginative. The writers sprinkle his dialogue with old Jewish guy jokes that only barely rise above dad humor. I didn't laugh at either impression.
I don't love Kate McKinnon's Hilary, nor Amy Poehler's, but I think they are more interesting. Both of them avoid pure mimesis. They attempt to dig into the unsettling combination of entitlement, calculation, and legitimate if over-indulged second-wave feminist rage that defines her psychology. They still go for the easy jokes, but Poehler's cackle and McKinnon's unpleasant smile speaks to what we think lies beneath Hillary's mask, not so much what exists on the surface. They're not as good as the legendary caricatural performances from American film history, Charlie Chaplin's version of Hitler, Peter Sellers's riff on von Braun or George C. Scott's riff on LeMay, but they take a risk, and they try to get at something that we should fear in a woman who still stands a good shot of being the most powerful leader in the world.
That's the aesthetic argument against Fey's Palin. There might be a moral argument against Fey's performance, inasmuch as it answers the horror represented by Palin's American fascism with a brand of anti-intellectual humor. Fey and the SNL writers attack Palin's body. They don't go after her terrifying mind.